Telephone system



April 1, 1930. L. 1.. RUGGLES 1,752,543

TELEPHONE SYSTEM Filed June 20, 1927 '7 Sheets-Sheet l Lava l Frau BOA/F0 (an: m5)

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L. L. RUGGLES TELEPHONE SYSTEM Filed June 20, 1927 7 Sheets-Sheet las April 1, 1930. 1.. L. RUGGLES 1,752,543

TELEPHONE SYSTEM Filed June 20, 1927 7 Sheets-Sheet 3 April 1', 1930. L. L. RUGGLES 1,752,543

TELEPHONE SYSTEM Filed June 20, 1927 7 Shets-Sheet 4 In u's i' n ur Lennard L. Fugglas April 1, 1930. L. L. RUGGLES TELEPHONE SYSTEM Filed June 20. 1927 7 Sheets-Sheet 5 (s55 we. 7)

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Filed June 20, 1927 7 Sheets-Sheet 7 I I, L

Imran m Leonard LE1; 125

Patented Apr. 1, 1930 UNITED STATES PATENT OFFICE LEONARD L.- RUGGLES, OF WHEATON, ILLINOIS, ASSIGNOR TO RESERVE HOLDING COMPANY, OF KANSAS CITY, MISSOURI, A CORPORATION OF DELAWARE 'rnnnrnonn SYSTEM The present invention relates to telephone systems in general, but is concerned more particularly with semi-automatic telephone systems, although certain of its features are not confined specifically thereto. 1 r

The main object of the invention is the production of new and improved circuit arrangements whereby connections between manual lines entering an exchange may be set up by automatic switches under the control of an operator at a switchboard in a remote exchange. 5

It is a further object of the invention to provide this service in an exchange terminati-ng lines of the local-battery magneto type without altering in any way the condition under which magneto lines operate when they terminate in the usual type of magneto manual switchboards.

The invention is especially suitable for application toa cluster of small villages and rural population centres, in which case several semi-automatic magneto exchanges may be each connected by one or more trunk lines with an operating center, usually located in a town or city'centrally located with respect to the area served by the several semi-automatic magneto exchanges.

The invention will be described hereinafter as applied to a system including a semi-automatlc magneto exchange having less than 100 lines terminating therein, there being a single operating trunk connecting the toll center with this'oflice, over which trunk the operator is automatically signalled when calls are made and over which she operates the automatic switches to complete desired local connections.

In order to provide for the setting up of connections from the semi-automatic magneto exchange toother'exchanges, 'orforsetting up connections inthe opposite direction, one or more toll trunks, in addition to the operating trunk, may be provided between the toll center and the semi-automatic magneto exchange, which for convenience will be referred to hereinafter as a S.A.M.X. V i

"A further object of the invention is the production of suitable circuit arrangements whereby the seizing of a connector in the 1927. Serial No. 195,917.

s.A.M.X. and the releasing of the connector, after it has been operated under the control of the operator, are accomplished responsive to the initial ring and the ring-01f of a magneto subscriber respectively. From this it will be understood that a connector after it has been seized by an individual lineswitch responsive to the operation of the calling hand generator, maintains the lineswitch locked in operated position until the release of the connector takes place when the calling subscriber again turns his hand generator, after he has replaced his receiver upon the termination of the conversation.

A further object of the invention is to provide a suitable finder switch for finding and connecting the operating trunk with any connector that has been seized. According to a feature of the invention, a new and improved relay-type finder switch has been provided in place of a progressively-movable mechanism, owing to the fact that the finder must operate once for each call made, as a relay-type switch has a much longer life un der heavy usage than a progressively-movable mechanism.

A further object of the invention is the provision of suitable arrangements whereby either of the two toll trunks provided may be used in an emergency as an operating trunk in case the operating trunk is defective or broken.

Accordingto'another'feature of the invention, an emergency operating set is provided in the S.A.M.X. so that an operator may control the automatic switches from that point during such times as all lines are down between the S .A.M.X. and the operating center, such as, for example, following a heavy sleet storm, or the like. f

A further object of the invention is concerned with the provision of suitable arrangements at the power board in the.

S.A.M.X. for causing the finder associated wit-h the operating trunk to connect the operating trunk with the power board and give the operator a special signal in case an abnormal condition exists, such as, for example, a

blown fuse, or the failure of the charging de 7 vice to operate properly, etc.

According to another feature of the invention, suitable arrangements have been provided for automatically releasing a connection after it has been established a predetermined. length of time. This is especially advantageous in view of the fact that subscribers do not always ring oil when they are through conversing.

Another object oi the invention is the provision of suitable arrangements whereby the operator at the toll center can operate either oi. the two toll connectors to complete a connection to any one o'l. the local connectors to determine whether or not it is operated and to release the connector if it is in an operated position and not in use.

Another object is the production of suitable circuit arrangements whereby the operator can operate a connector and its associated code selector to cause ringing current to be sent back over the calling line, when the called substation is on the same line as the calling substation.

There are other objects and features of the invention which are mainly incidental to the carrying out of the objects and features above mentioned. The various objects and features of the invention can be understood best from a further perusal of the specification in connection with the accompanying drawings, comprising Figs. l8.

Referring now to the drawings, they show by means of the usual circuit diagrams a uliicient amount of equipment in a system embodying the features of the invention to enable the invention to be understood and carried into practice. Figs. 17 are circuit diagrams and Fig. 8 is a lay out of the sheet on which Figs. 1-7 are draw showing the way in which the sheet should be. assembled in order that they may be understood best.

Fig. 1 shows an operating trunk and two toll trunks connecting the manual ofl ice on the left (used as the operating center) with the SALLX. including the equipment shown on the right of Fig. 1 and in Figs. 27. It will be noted that part of the equipment at the manual exchange is at a toll board and part of it is at a local board. The operator atthe toll board handles the toll connections with the S.ri.i\I.X., and the operator at the local board handles the local trafiic and also supervises the connectors in the S.1*\.M.X. periodically, to see that they are not lofted-normal after being used. The equipment on the right-hand side of Fig. l is trunkswitching equipment used when necessary to switch the operating circuit from be operating trunk to one of the toll trunks in case the operating trunk out of order.

F 2 shows the rela -type tinder and its an). liary equipment as ciated with the opcrating trunk for the purpose oi. connecting the operating trunk to any local connector that is taken for use. i

Fig. 3 shows the local connector No. 1, there being ten such connectors. This drawing shows also the line of substation A and the associated lineswitch LS, together with the master switch common to all the lineswitches. This drawing shows also a timing device individual to the associated connector for limiting the time during which the connector may remain operated.

Fig. 4 shows the wipers and a portion oi the banlr contacts of the local connector No. 1, together with the code selector CS1 individual to the local connector No. 1. This drawing shows also the substation l3, accessible to the connectors.

Fig. 5 shows the toll connector No. 1 which terminates the toll trunk No. 'l, l. The bank and wipers of this tell connector are shown in Fig. 6, which shows also the code selector CS2 individual to the toll connector No. 1. This drawing shows also the code generator CG. This generator is a motordrivcn drum, having a number of brushes and insulating and conducting segments as shown. The showing of the drum has been developed into a plane instead of a cylinder, in order that it may be understood better. The drum rotates in the direction indicated by the arrow.

Fig. 7 shows the power board and the associated power-supervisory relays. The power board includes the charging apparatus and the two storage batteries used to supply current for the operation of the appa. 'atns in the S.A.M.X. It is to be noted that separate battery symbols and ground symbols are used throughout the drawings. It is to be understood that all ground symbols in the S.A.l'd.X. indicate a connection to the grounded bus bar 714 at the power board, and that all battery symbols indicate a connection to the battery bus bar 713. Fig. 7 shows also the emergency set in the S.A.M.X. This set is provided so that an operator may be despatched through the S.A.M.X. to control the switches through this emergency set, in case the lines are down between the SAIVLX. and the operating center.

The apparatus having been described gen. erally, a detailed description oli its operation will. now be given. For this purpose it will be assun'ied that the subscriber at substation A, Fig. l, desires to converse with the subscriber at substation B, Fig. 4.

Call from substation A, Fig. 3, i0 substation B, Fig. 4

In order to signal the operator at the operating center, the subscriber at substation A operates his hand generator to t'ansmit ringing current over his line, after which he removes his receiver so as to be able to converse with the operator when she responds. Responsive to the ringing current, relay 302 operatesand closes a circuit for the slowacting relay 301. 'Relay'30l operates and closes a circuit through the pull-down winding of the lineswitch. This circuit includes the open-main conductor which is common to all the lineswitches. This open-main conductor passes through certain contacts in the master switch and receives its current through the terminal 750. The two terminals 750 in Figs. 3 and 7 are joined together and the battery supplied to the open-main conductor is taken through the low-wound supervisory relay 727, Fig. 7, for a purpose to be explained hereinafter. Then the pull-down winding 303 is energized, the plunger of the lineswitch is caused to enter the bank, and the cut-oft armature is operated to disconnect relay 302 from in bridge of the calling line. When the contacts of the lineswitch are closed upon the entry of the plunger, a holding circuit is closed for the cut-ofi winding 304 of the lineswitch from the grounded release-trunk conductor 376, this conductor being grounded at the contacts of relay 313. This circuit is effective in maintaining the lineswitch operated after the slow-acting relay 301has fallen back. As a further result of the plunger entering the bank, the talking conductors of the line are extended into connection with the corresponding conductors of thelocal connector No. 1, and ground from the grounded release trunk conductor 376 is extended through the lineswitch contacts to the combined lineswitch-hold and motorswitch test conductor 377 and through the master-switch wiper 343 for the upper winding ofthe master-switch test relay. A circuit is also closed over hold conductor 377 for relay 306 in the connector. Relay 306 operates and closes one point in the circuit of chain relay 341 in the master switch and .places ground on the auxiliary test conductor 378, thereby closing a circuit for the lower winding of the test relay in the master switch. The master switch test relay operates from either winding and causes the master switch to advance in the usual manner to pre select another idle connector. During the advance of the master switch, the connection between the exchange battery and the openmain conductor is held open in the usual manner.

As a further result of the grounding of the hold conductor 377, hold relay 307 operates and opens at its inner upper armature a point in the circuit of release magnet 321; at another upper armature, it grounds the local locking conductor 328; and at its lower annature it closes a circuit for relay 345 of the five-minute timing device for a purpose to be explained in detail hereinafter. As a result of'the grounding of the locking conductor 328, a circuit is closed through the inner upper armature of relay 318 for relay 319. Relay 319 operates and shunts relay 319 for aipurpose which will laterappear.

Asa further result of the operation of re: lay 307, it grounds the common start conductor 221 and the individual stop conductor 222 at its two upper armatures. As a result of the grounding of the start conductor, a circuit is closed for start relay 205, Fig. 2, of the relay-type finder. Relay 205 operates and places ground on locking conductor 219 at its lower armature, at its upper armature it connects the grounded interrupter 217 to the impulsing conductor 218. This impulsing conductor extends normally through the chain of contacts shown to relay 213. It may be pointed out at this time, that the relay pairs corresponding to connectors 29 are a omitted in the drawing and that they are, in practice, included in the circuit between relays 209 and 210, at the point indicated by the dotted portion of the connecting conductors. As soon as interrupter 217 closes, relay 213 operates and locks itself through relay 212 to the locking conductor 219. Relay 212 does not operate immediately owing to the fact that it is short circuited through the interrupter 217. lVhen the interrupter 217 opens, the initial circuit of relay 213 is broken, whereupon the locking circuit through relay 212 becomes effective and relay 212 operates, relay 213 remaining operated. When relay 212 operates it opens at its lower armature a point in the circuit of the nonoperated relay 206, and at its upper armature it shifts the impulsing conductor 218 from relay 213 to relay 211. Relay 211 accordingly operates when the interrupter 217 closes the next time and it locks itself through relay 210, with the result that relay 210 operates as soon as the interrupter 217 opens again. Relay 210, it will be noted, opens the circuit of relays 212 and 213, whereupon these relays fall back.

This operation continues in the manner described until the common stop conductor 220 is connected by a relay similar to relay 211 or relay 213 to an individual stop conductor, such as conductor 222, which is grounded. Since the instant call is coming in over local connector No. 1, and since local connector No. 1 corresponds to relay 206 and 207, which are last to be operated, the operation continues until relay 207 operates following the operation of relays 209 and 208. When relay 207 operates, it looks itself to locking conductor 219 through relay206 and the lower armature of relay 212, which relay was restored upon the operation of relay 210. As a further'result of its operation, relay 207, at its lower armature, connects up the individual hold conductor 226 to the common hold conductor 231, and at its inner-lower armature it connects the individual stop conductor 222, previously grounded in the local connector No. 1, to the common stop'conductor 220, thereby closing a circuit throughth'e contacts of relays 204 and 203 for stop relay 201. Relay 201 operates and disconnects interrupter 217 from impulse conductor 218 at its middle upper armature, thereby stopping the transmission of impulses. This results in the opening of the initial circuit of relay 207, whereupon relay 206operates in series with relay 207 and opens the circuit of relays 208 and 209, which fall back, and relay 208 transfers the impulse conductor 218 back to relay 213. As a further result of the operation of stop relay 201, it closes a circuit for relay 202 at its inner-upper armature, which circuit will be traced subsequently. At its upper armature relay 201 places a multiple ground on start conductor 221, and at its lower armature, it places ground on the common hold conductor 231, thereby grounding the individual hold conductor 226 through the lower contacts of relay 207. When this 1 occurs a circuit is closed through contacts of relay 318, Fig. 3, for hold relay 309. Hold relay 309 ope ates and connects up the talking conductors 223 and 224 of the operating trunk to the corresponding conductors of the connector, at its upper and lower armatures.

As a further result of its operation, relay 309, at its inner lower armature, prepares a circuit for the vertical magnet 320, and at its middle lower armature it opens the circuit of the relay in the associated timing device for a purpose to be explained hereinafter.

In the ope1atiug-trunk equipment. Fig. 2, relay 202 now energizes in a circuit from the exchange battery through its winding, contacts of relay 201, mid-point of the left-hand repeating-coil windings, the two trunk conductors in parallel, contacts of the key EK, contacts of relay 121, inter-e:-;changc portion of the operating trunk, contacts of the transfer keys T1 2 and T111, right-hand repeating coil windings in the operating center, contacts of the answering and release key 104, contacts of relay 102, and the winding of relay 101 to ground. 1 hen relay 202, Fig. 2, operates over this circuit, it opens a point in the impulse circuit at its lower armature and at its inner armature it closes a circuit for release relay 203. It prepares the impulse circuit at its lower armature; at its inner lower armature, it closes a locking circuit for stop relay 201 and opens its initial circuit; relay 204 responds to the closure of its circuit by relay 203 and opens a further point in the initial circuit of stop relay 201, for a purpose which will later appear.

In the operating center, relay 101, Fig. 1, pulls up in the line circuit above-traced over the operating trunk and through relay 202, Fig. 2, lighting the associated call lamp. \Vhen the operator notes the lighted condition of this lamp, she operates her key 104 into answering position, connecting the associated talking conductors to her telephone circuit. As a further result of being thrown into answering position, the key 104 connects the common dialing conductor 105 to the opcrating leg of the operating trunk, at the same time disconnecting relay 101. Relay 101 now falls back and extinguishes the call lamp, the current flow over the operating trunk being continued through the calling device CD1. As a further result of the operation of key 104, a circuit is closed for relay 103, whereupon relay 103 operates and locks itself through release contacts of the key, closing at its upper armature a circuit for relay 102. Relay 102 operates and opens a further point in the circuit of relay 101, at the same time closing a circuit for the busy lamp.

The operator now converscs with the calling subscriber and ascertains the desired number. Upon learning this number, the operator manipulates her calling device CD1 in accordance with the digits thereof. Upon reference to Fig. 4 it will be noted that the line of substation B terminates in the third set of contacts in the eighth level. The line number is therefore 83. It is assumed that code No. 5 is assigned to substation B, in which case the complete number is 83-5.

When the calling device CD1 is operated in accordance with the first digit 8, eight interrupt-ions are produced in the circuit of relay 202, Fig. 2. As a result relay 202 falls back momentarily eight times. Each time it falls back, relay 202 grounds the impulse conductor 223 at its lower armature, thereby transmitting eight impulses of current over this conductor to the vertical magnet 326 of local connector No. 1, Fi 3. The im )ulse path, at the time of its init1al closure, includes contacts of relay 309, normally closed oll'- normal contacts, including 51311110 325, and relay 314. By the Operation of the vertical magnet, the wipers 401-403 of the connector are raised step-by-step until they arrive opposite the eighth level of bank contacts. Relay 314 operates in response to the first impulse of current, and, being slow-acting, remains operated throughout the vertical movement. At its lower armature, relay .314 opens a point in the circuit of the rotary magnet 327 and prepares a new circuit for itself and for the vertical magnet which becomes effective upon the shifting of the associated off-normal contacts at the end of the first vertical step. WVhen the first impulse is received, cut-ofi relay 309 is operated from two sources; its upper winding is energized from the upper con tacts of series relay 314, and its lower winding is energized from off normal contacts 305 in multiple with the lower winding of chaincontrol relay 306. This double arrangement is provided to render more remote the chance of failure of the relay to operate. Upon operating, relay 310 locks itself to conductor 328 at its inner upper armature; prepares a release-on-busy circuit at its lower armature;

and at its two uppermost armature removes ground from start conductor 221 and stop conductor 222, leaving start conductor 221 grounded at the upper armature of relay 201, Fig. 2. The ungrounding of the stop conductor 221 prevents the reseizure of the connector by the operating-trunk equipment until the connector has been released and again seized by a lineswitch.

Then the stop conductor is ungrounded,

relay; 204, Fig. 2', falls back and closes a point in the stopping circuit of stop relay 201,*now held operated by relay 203.

At the end of the vertical movement, relay 314 falls back and shifts the impulse con- 4, are rotated into engagement with the bank contacts terminating the line of substation B. Slow-acting change-over relay 316 is energized in multiple with rotary magnet 327 throughout the rotary movement. At its upper armature, it disconnects the test-wiper conductor 354 from the upper winding of switching relay 317 and connects it instead, through contacts of relay 317, to busy relay 315, and at its inner lo'wer armature it closes a shuntaround the corresponding contacts of busy relay 315 so as to prevent a premature opening of the rotary-magnet circuit in case test wiper 402 shouldencounter busy test contacts during the rotation of the connector and thereby operate busy relay 315.

The operation taking place at the end of the rotary movement of the connector is dependent upon the busy or idle condition of the called line. Assuming first that the called lineis busy, test wiper 402 encounters armature it connects the busy lead to the lower talking conductor through the lower contacts of relay 315. In this way the busy tone 1s transmitted to the operator over the operatingtrunk and to the calling subscriber over his line. Upon hearing this busy tone, the

calling subscriber is expected to replace his receiver'and call again later. \Vhen the operator clears out, the connector is released by the hereinafter explained operation of relay 313 when its circuit is closed at the middle lower armature of relay 309. This circuit includes the lower armature of the operated relay 308 and a lower armature of the non-operated relay 317.

Assuming now that the line of substation is idle whencalled, busy relay 315 is not operated when the wipers of the connector come to rest upon the contacts of the called line, and a circuit for the upper winding of relay- 317 is closed at the upper armature of relay 316 when it falls back. This circuit extends from ground on the grounded locking conductor 328 through the upper armature normal, of relay 315, upper winding of relay 317, upper armature of relay 316, conductor 354, test wiper 402, test contact of the called line, and conductor 417 to battery through the cut-off winding of the lineswitch (not shown) belonging to the called line. This winding corresponds to cut-ofl' winding 304 of the lineswitch LS,Fig. 3. The cut-01f armature of the called lineswitch operates to remove {he associate line relay from across the called In the connector, Fig. 3, relay 317 operates through its upper winding, and at its inner lower armature closes a locking circuit for itself to the grounded locking conductor 328. At another lower armature, it disconnects the operating conductor from rotary magnet 327 and extends it to conductor 355; at still another lower armature, opens a point in the circuit of the forced-release relay 313 so as to prevent a premature release when relay 309 subsequently falls back upon the disconnecl tion of the operating trunk from the connector; it prepares a so-called ring-back circuit at its lower-most armature through the associated condenser of small capacity; it opens a further point in the circuit of busy relay 315 at its inner upper armature; and at its upper armature it closes a direct connection between the grounded locking conductor 328 and the test-wiper conductor 354 so as to busy the called line over a circuit path excluding its own upper winding.

Having set the connector on the contacts of the called line, the operator now dials the code-selecting digit 5 in order to operate the code selector CS1, Fig. 4, to select the. code assigned to substation B. \Vhen this lastdigit is dialed, five impulses of current are transmitted to the stepping magnet 409 of the code selector CS1 over conductor 355 and through series relay 406. In response to these five impulses, the stepping magnet 409 of the code selector CS1 advances the wipers 411 and 412 step by step until they rest upon the shunts the inner contacts of oifnormal re lay 405 so as to maintain the operating circuit intact after the off-normal 405 operates upon the first off-normal movement of the wipers of the switch. After the last impulse has terminated, relay 406 falls back and opens the operating circuit. A locking circuit for relays 407 and 408 is prepared at the lower armature of relay 405, and a pick-up circuit is now prepared through the middle armature of relay 405 and the lower armature of relay 406 for pick-up relay 407. Now, as soon as the code generator CG, Fig. 6, arrives in the position shown in the drawings, ground through the ground-feed wiperis placed on the pick-up conductor. This closes a circuit for pick-up relay 407 in the code selector CS1, Fig. 4. Relay 407 operates and locks itself through the lower armature of relay 405, at the same time opening its initial circuit. At its middle lower armature, relay 307 connects the common stop conductor to the individual stop conductor 356, preparatory to advancing the circuits from ringing position to talking position. As a further result of the operation of pick-up relay 407, ringing conductors 352 and 358 are connected up at the upper and lower contacts of this relay to the wipers 411 and 412, with the result that the code corresponding to the setting of these wipers is placed on these conductors and on the called line, as will be discussed subsequently.

Returning now to the operating center, Fig. 1, the operator, after having dialed the desired number waits only long enough to hear the so called ring back tone, which indicates that the line is being signalled, and then operates her key 104 into release position. In this position of the key, the operating conductor connected to the midpoint of the associated right hand repeating coil windings is connected hack to the branch normally extending to ground through relay 101. This branch, however, is now open at the contacts of relay 102 and also at the contacts on the release key, as a result, line relay 202, Fig. 2, falls back and releases the connection between the operating trunk and the connector in a manner to be pointed out shortly.

'Key 104, at its lower left contact, opens the locking circuit of slow-acting relay 103. Relay 103 falls back after a slight interval and opens the circuit of the slow-acting relay 102. Slow-acting relay 102 falls back after a slight interval and opens the circuit of the busy lamp at its lower armature, at the same time preparing a circuit for relay 101 at its upper armature. The operator now restores her key 104 to normal, as the operating trunk has been disconnected from local eonnector No. 1 in the S.A.M.X. during the time required for relays 103 and 102 to fall back, as will now be pointed out.

WVhen relay 202, Fig. 2, falls back responsive to the opening of its circuit by key 104, Fig. 1, it again grounds the impulse conductor 225, but no operation is effected owing to the fact that this impulse conductor is open in the code selector CS1, Fig. 4. At its inner armature, relay 202 opens a circuit for the slow-acting release relay 203, and relay 203 falls back after a slight interval and removes ground from impulse conductor 225 at its lower armature, at the same time open ing the circuit of relay 201 at its inner lower armature. Relay 201 thereupon falls back and removes ground at its lower armature from the hold conductor 231. As a result of relay 201 falling back, the grounded interrupter 217 is again connected up through the upper contact of relay 205 to the impulse conductor 218. The operation of the relays of the finder is again started, but since the start conductor 221 is ungrounded at the upper armature of relay 201, relay 205 falls back immedi ately and stops the operation of the finder and releases the operated relays, unless start conductor 221 has in the meantime become grounded from another calling connector.

As a result of the removal of ground from the common hold conductor 231 by relay 201, ground is removed from the connected branch holding conductor 226, and hold relay 309 of the connector, Fig. 3, falls back and disconnects the talking conductors of the connector from the operating-trunk talking conductor 223 and 224 at its upper and lower armatures. At its inner lower armature, it opens a further point in the local branch of the operating conductor 225, and at its middle lower armature it again closes a circuit for relay 345 of the associated counting device, whereupon the device is again started to time the length of the conversation in a manner to be pointed out hereinafter.

Returning now to the established connection, the wiper 412 of the code selector CS1, Fig. 4, is now grounded and the wiper 411 is connected to the code conductor. There a connection over the lower contacts of relay 407 and conductor 358 between the grounded wiper 412 of the code selector and the lower wiper 403 of the connector. This connection includes the lower armature, normal, of relay 318, and conductor 357. There is a similar connection between wiper 411 and the upper talking wiper 401 of the connector. This latter connection includes the upper contacts of relay 407, conductor 352, one of the upper armatures, normal, of relay 318, and conductor As a result, the ringing current placed on the No. 5 code conductor is transmitted out to the called line over wiper 401 of the connector and it returns to ground over wiper 403. Upon referring to the code generator CG, Fig. 6, it will be noted that the code corresponding to conductor No. 5 is live rings. These five rings are preceded by a long warning ring. The reason for this arran gement is that the code is transmitted only once and the long attention ring is placed on the line ahead of the regular code so that the subscribers will all listen while the code is being transmitted. The way in which this code, together with the long attention ring, is placed on the code conductor No. 5 from the associated ringing current source through the brushes of the cod-e generator appears to be obvious from the drawings. It may be pointed out, however, that the conducting segments of the drum are not connected to any current source or connected together in sets except as shown by the connecting conductors, indicated as being on the face of the drum. Actually, these conductors may be embedded Within the drum instead of being on the face thereof.

After the last ring of the code has been delivered, the stop'conductor is momentarily grounded when the last segment in its path is encountered by the stop brush on the code generator. When the stop conductor is grounded, a circuit is closed through the middle lower armature of pick-up relay 407, Fig. 4, for stop relay 408. Relay 408 energizes and locks itselfto ground through the lower contacts of off-normal relay 405. Release magnet 410 is energized in multiple with relay 408 and in series with the low-wound supervisory relay 736, Fig. 7. WVhen the release magnet operates, the code selector releases to normal position and oil-normal relay 405 falls back and unlocks relays 407 and 408, also opening the release magnet circuit.

A circuit is completed (when the stop conductor is grounded) over conductor 356 for the ring-cut-off relay-318 of the connector, Fig. 3. Relay 318 operates and locks itself to the grounded locking conductor 328 at its inner upper armature, at the same time opening its initial circuit and opening the circuit of slow-acting relay 319. At its lower armature and at one of its upper armatures, it disconnects the wipers 401 and 403 of the connector from the wipers 411 and 412 of the code selector CS1, and connects its wipers to the incoming talking conductors of the connector so as to complete the talking circuit to the called line. At its upper armature, relay 318 places the ring-0E relay 320 across the upper and lower talking conductors of the connector, so as to place the release of the connector under the control of the calling line, and at another of its upper armatures it disconnects relay 309 from the holding conductor 226, whereupon relay 309 falls back and disconnects the talking conductors of the connector from the corresponding conductors lay 318, it is short circuited by the contacts on slow-acting relay 319. Slow-acting relay 319 remains operated for an interval and maintains the short circuit around relay 320 for a suflicient time to permit any charge that. 4 maybe onthe talkingconductors of either the calling or the called line to leak oil before the short circuit is removed. This is specially valuable in case the ringer at the called substation has a condenser in series with it, in which case the condenser may have retained a charge at the end of the last inipulse of ringing current transmitted to the called line.

' When the subscriber at substation B responds to the code assigned to his substation I by removing his receiver, the conversation may take place in the usual manner. lVhen the conversation is terminated, the subscribers at substations A and B replace their receivers. The subscriber at substation A, being the calling subscriber, rings off by operating his hand generator momentarily in the usual manner. The momentary impulse of ringing current thus generated operates relay 320 of the connector. Upon operating, relay 320 closes a circuit from the grounded locking conductor 328 for slowacting relay 311. Relay 311 operates and closes a circuit for the slow-acting relay 312. Relay 312 operates and prepares a circuit for the slow-acting release relay 313, when the impulse of ringing current is terminated. Relay 311, which is slow-acting so as to enable it to hold up while relay 320 is vibrating in response to ringing current, now falls back and closes a circuit for relay 313 through the contacts of relay 312, at the same time opening the circuit of relay 312; Relay 313 operates and remains operated until relay 312 falls back, after which relay 313 again restores. During the time that relay 313 is operated, ground is removed at the contacts of relay 313 from release trunk conductor 376. When this ground is removed, the current flow ceases in the bridge-cut-otf and holding winding 304 of the lineswitch LS, in the upper winding of relay 306 of the connector, and in the winding of relay 307. \Vhen this occurs, the lineswitch LS releases and relay 307 of the connector falls back. Relay 306 remains operated for the time being due to the current flow through its lower winding from the off-normal contacts 405. hen the lineswitch LS releases, the connection with release trunk conductor 376 is broken, so that the private normal conductor of the line and the holding conductor 377 of -the connector are not again grounded when ground is replaced on the release trunk conductor 376 by relay 313. i

As a result of the deenergization of holding relay 307 of the connector, ground is removed from the grounded locking conductor 328, whereupon the locked-up relays 317 and 318 fall back. Relay 308 does not fall back at this time owing to the current flow through its lower winding in multiple with the lower winding relay 306. As another result of the deenergization of relay 307, a circuit is closed at the inner upper contacts of this relay .net 321 is opened.

tacts 305, open, relays 306 and 308 fall back.

Relay 306 renders the connector selectable again to the associated master switch by removing ground from test conductor 378 at its lower armature.

The connection is completely released and the apparatus involved therein is in readimess to be used in setting up other connecions.

Revertin-g ca Zls It will now be assumed that the subscriber at substation A desires to call another subscriber whose substation is connected to the same line, the other substation being signalled by a code different than that of substation A. It will be assumed further that the local connector No. l is the one seized by the lineswitch LS when the receiver is removed. That being the case, the connection is C0111- pleted as before described between the operating trunk and the local connector No. 1 by the relay-type finder shown in Fig. 2.

lVhen the operator responds and is informed that the calling subscriber desires to complete a connection to another substation on the same line, the operator sets the connector by dialing the digits 7 and O (the reverting call combination), after which she sets the code selector CS1, Fig. 4, in accordance with the code assigned to the called substation on the calling line. The operator requests the calling subscriber to replace his receiver and wait until the code of the called subscriber has been transmitted before removing the receiver again, as part of the ringing current would be shunted away at substation A otherwise, and also, disagreeable noises would be produced in the receiver by the ringing current.

It may be pointed out that the No. 70 localconnector hank-contact set are left without multipling conductors to avoid interference in case two or more reverting conversations are carried on at the same time.

\Vhen the wipers are set on the 70 bank contacts, by impulses transmitted over conductor 225 under the control of the operator in the hereinbcfore described manner, the 70 spring contacts 324: are closed, whereupon the reverting call relay 310 operates. Upon operating, relay 310 at its upper and lower armatures opens the talking connection between the operated connector and the operating trunk so as to prevent the ringing current, to be applied subsequently, from reaching the operating trunk, in case the operator has not disconnected at the time the ringing current is applied. At its inner-lower armature, relay 310 prepares a circuit for relay 313 so as to enable the connector to be released at the termination of the ringing period.

As mentioned hereinbefore, the 70 contacts are left unmultipled. The 70 contact in the bank of test wiper 402, however, is connected to battery through a resistance so as to afford a circuit for the test winding of relay 317 when a reverting call is made. The corresponding contacts in the other connector banks are similarly connected to battery, each through a separate resistance.

Vvhen the connector has been set, relay 317 operates through its upper winding and through the test wiper 102, which encounters a battery potential on the contact on which it is set on account of the above mentioned individual resistance. Relay 317 performs a switching operation as hereinbefore described, including the switching of the impulse conductor from rotary magnet 327 to impulse conductor lVhen the operator dials the code-selecting digit, the code selector CS1 is operated over conductor 355 in accordance with the code assigned to the called substation. At the end of the operation of the code selector, relay 100 falls back as hereinbefore described and con nects up the pick-up relay, with the result that pick-up relay st07 operates and connects up the wipers 411 and 112 of the code selector. Following the operation of the pick-up relay, the ringing current is transmitted over conductor 352 from the wiper 1-11 and returns to ground over conductor 358 and wiper 412. Since the bank contacts on which the wipers 401 and 4.03 of the connector are standing are left dead, the ringing current does not take this path at this time. Instead, the ringing current passes through the upper and lower armatures of the reverting call relay 310 and thence back to the calling line, thereby operating all the ringers on the calling line.

After the ringing current has been transmitted, stop relay l03 of the code "elector CS1 operates and locks itself in the hcreinbefo-re described manner with the result that the code selector is restored to normal. At the same time, the hereinbefore'described impulse of current is delivered over conductor 356 to the ring-cut-off relay 318 of the connec' tor, with the result that relay 31 J operates and performs the switching operations hereinbefore described. At this time, since relay 310 is operated, a branch circuit is closed over i conductor 356 through operated contacts of relay 310 and jumper 379 for release relay 313. Release relay 313 operates at this time and releases the connector in the hereinbefore described manner, leaving the two subscrilr lOC LIJ

ers on the line of substation A free to converse without having any centraleoffic'e equipment tied up.

The calling subscriber, as Well as the called subscriber, hears the code of the called subscriber and he removes his receiver after the code has been transmitted, with the result that the two subscrioers may converse as soon as the called subscriber responds, Thecalling subscriber is instructed to not ring off at the termination of r verting calls, as. this would operate the lineswitch LS and signal the operator needlessly.

It will be noted that the line of substation A is unguarded after the connector has been released and is therefore unguarded during conversation. In some localities, the subscriber-s object to, this unguarded feature owing to the fact that a line-is called occasion: ally while two subscribers are conversing in a reverting connection with the result that the line is intruded upon and withthe further result that the application of ringing current while they are talking often results in very annoying noises in their receivers. In this case,.arrange1nents are made so that the line renurins guarded during conversation. This is accomplished by merely omitting the jumper 3.79, Fig. 3, in which case the release re.- lay 313 is not operated upon the release of the code selector- CSl at the end ot the application of ringingcurrent. hen this jumper is omitted, the subscribers are instructed to ring of at the end of reverting calls as well as at the end of other calls. he connector is then released at the end of the conversation in the hereinbefore manner;

Operation 0 f timing device In a system of this nature, it often happens that a subscriber finishes a conversation and leaves his telephone without rings ing off. In this case the connector is left operated and cannot be used by anyone else until it is released. In order to provide for the release of connectors left operated in this manner and in order to provide for the release of lineswitch'es in case a subscriber calls and receives no. response fromthe operator, a timing device has been provided individual toeach connector. A timing. device individual to' the local connector No. 1 is shown in Fig. 3 and is labeled 5-.Minute timing device. This timing device is arranged to complete its operation and release a connection five minutes after it is started. This time of course is. purely arbitrary and may be set at any other interval.

Assuming now thatthe connector shown'in 7 Fig. 3 is seized by a lineswitch such as LS, the

holding relay 307 is operated over hold conductor 377 in the liereinbcfore described manner, closing a circuit for relay 345: of

r, the timing device through the-O"-level shaiit contactsand the middle lower armature of relay 309. Relay 345 operates and closes a circuit for stepping magnet 347 of the timing switch through the 30-second interrupter 346, common to the several timing devices. Every thirty seconds, this circuit is 001111 pleted and opened again by the common in-. terrupter with the result that stepping magnet 347 operates once each thirty seconds, advancing the Wipers 350 and 351 one step each time it operates. Ordinarily, relay 309 is operated upon the response of the operator after the connector has been found by the finder shown in Fig. 2, whereupon the relay 345 falls back and releases the. counting de-, vice by closing a circuit, for release magnet 348 through the off-normal contacts 349. Assuming, however, that the call is not taken care of for some reason, the advance of the wipers 350 and 351 continues until wiper 350 reaches its tenth bank contact,- at the end of approximately five minutes; When iper 350 reaches its tenth contact, itcloses a circuit for relay 313; Relay 313 operates and removes ground from release trunk; con; ductor 37 6, whereupon the linesw-itch LS restores to normal and relay 307 falls back, When relay 307 falls back it opens the circuit of relay 345, whereupon the timing device releases through the action of magnet 348, and relay 313 restores when its circuit isopened upon the release of wiper; 350. The lineswitch LSre nains restored until the calling subscriber rings again to make another at; tempt at securing the desired connection.

Assuming now that a connection has been extended by the lineswitch LS to the local connector No. 1 and that the operator has responded and operated relay 30.9, the relay 345' is released in the hereinbetore described manner, at the middle-lower armature of. relay 309. The timing device remains at rest until the connector and the code selector have been operated and until the operating trunk has been disconnected from the local connector, at which point relay 309 falls back and again establishes a circuit for relay 3455; Upon the operation of relay 345 the timing device operates one step every thirlty seconds as before deseribed.- After the conversati'on has proceeded for approximately four minutes (assuming that the conversation lasts this long), wiper 35l comes-into engagement with its eighth; associated contact. This occurs at a time when stepping mag.- net 34-7 is energized, and the stepping magnet remains energized for a few seconds while the interrupter 346 is passing through its closed position. it-h the stepping magnet energized and with the wiper 341 on its eighth contact, a circuit is closed from the commonwarning-tone generator to the lower talking conductor.- In thisway, this tone is heard by the conversing.subscriber and they are thereby warned that the connection will exist for only about another minutea It will be noted that the warning-tone generator is merely a transformer having an interrupter for interrupting a battery circuit through its primary winding. The battery circuit is normally open and is closed only momentarily at spaced intervals. The result is a succession of clicks which lasts for a few seconds while the interrupter 346 is stepping through its closed position. These clicks are not close enough together nor of sufficient volume to interfere materially with the conversation. At the end of the closed period of the interrupter, magnet 3&7 falls back and opens the warning tone circuit.

If the connection is not released by the ring off before the timing device reaches its last position, the release is brought about by wiper 350 reaching its last contact and operating release relay 313. The lineswitch LS is released as hereinbefore described and the connector releases responsive to the deenergization of relay 307, which closes the release magnet circuit at its inner upper contacts.

It may be pointed out at this time that the release of the connector stops the conversation by disrupting the connection in case a regular call between two separate lines is being made, but the subscribers may continue to converse with one another if the call is a reverting call between two subscribers on the same line, the arrangement being intended more to free the equipment for use when it is being tied up due to subscribers forgetting to ring off than to limit the conversation time, although the latter result is of considerable utility. It will be noted that a line is unguarded after the connector has been released by the timing device and that subscribers on the same line who continue to converse run the risk of having their conversation intruded upon.

Two-number toll connection The way in which calls between a S.A.M.X. line and an outside line are completed, will now be considered. These connections fall into two classes, depending upon the origin of the call. Considering outgoing connections, they fall into two groups, depending upon the distance over which it is desired to converse. A connection set up to a line only a relatively short distance away is usually completed by the toll operator, while the calling subscriber waits for an answer, and is referred to as a two-number connection, while connections to lines still farther away are set up by the operator who re-rings the calling subscriber after she has the connection ready.

Considering first a two-number connection, it will be assumed that the subscriber at substation A desires to converse with a subscriber outside of his local exchange whose line terminates in a nearby exchange. The subscriber at substation A causes his lineswitch LS to seize an idle connector, local connector N o. 1, Fig. 3, for example, whereupon the operator is signalled in the usual manner. lVhen the operator responds and asks for the number, the subscriber replies long distance.

Upon learning that the calling subscriber desires a long distance connection, the operator observes the condition of the busy lamps associated at her position with the toll trunks. If both toll trunks are idle, she may dial the number assigned to either, but if one is busy, she dials the number assigned to the other toll trunk. If both toll trunks are in use, the operator informs the calling subscriber that long distance is busy.

Upon referring to Fig. 4, it will be noted that the first and second sets of bank contacts in the tenth level of the local connectors are connected by conductors to the No. l and No. 2 tell connectors, respectively. In this case it will be assumed that toll trunk No. 1 is idle and that the operator dials the number 01 assigned to this trunk. lVhen she dials this number, the local connector No. 1, Fig. 3, responds in the usual manner and sets its wipers 4014t03, Fig. 1, on the first set of bank contacts in the 0 level, being the contacts to which the conductors 113'115 leading to tell connector No. 1 are connected.

Upon. the shaft of the connector being raised to the tenth level, the 0-level shaft contacts 822, and 323, F ig. 3, are shifted. Contacts 322 remove the shunt from around the associated talking condenser for a purpose which will become apparent as the description progresses. At contacts 323, a point in the circuit of the timing-device relay 34.5 is opened, as it is not desired to use this timing device in connection with outside calls, and a circuit is prepared by contacts 323 in their shifted position for the lower winding of ring-cut-ofi relay 318.

When relay 316, Fig. 3, falls back at the end of the rotary movement of the connector and connects the test wiper conductor 35 1 to the ground through the upper winding of relay 317, relay 317 operates over test wiper 402 of the connector, Fig. 4:, and over private normal conductor 11 1 extending to toll connector No. 1, Fig. 5. Relay 317 closes its usual locking circuit and transfers the impulsing conductor to branch conductor 355 extending to the code selector CS1, Fig. at.

The operator releases the operating trunk from local connector No. 1, as before described, as soon as she has dialled the last digit 1 in the number assigned to the toll trunk No. 1. lVhen she does so, and impulse of current is transmitted during the releasmg operation over conductor 355 and operates the stepping magnet 409 one step durmg the time required for release relay 103, Fig. 2, to fall back after its circuit is opened by the impulsing relay 202. This operation on the part of the code selector CS1 is merely incidental, but as it does no harm it has been permitted to take place; Upon the termination of the impulse to the stepping magnet, relay 406 falls back followed by the energize-- tion of pick-up relay 407. The code corresponding tothejNo- 1 position ofthe code-Se le'ctor CS1 is placed on wiper 411 and is ex tended back over conductor 352, but thisringing current does not reach the line owing to the fact that ring cut-olf relay 318 is operated when relay 309 falls back, the circuit inclusl ing the middle lower armature" of relay lower armature of relay 307, and springs 323, shifted. The code selector CS1 is released in the hereinbefore described manner when the stop relay 408 pulls up.

When the test wiper 402, Fig. 4, is grounded at the end of the rotary movement of t-he'connector, as hereinbefore described, a circuit over conductor 414 is closed through the upper contacts of relay 507, Fig. 5, for relay 505, and a branch circuit is closed through the upper contacts of relay 503 for relay 501. llhis'is the circuit, it will be'remembered, over which the upper winding of relay 317 is operated. The upperwinding of relay 317 is short cir'cuited in' the usual manner to apply direct" ground to the test wiper 402 as soon as relay 417 operates'an'd' locks itself at its inner lower armature. When relay 5'05 operates, it switches the talking conductors associated with the right-hand repeating-coil windings from the talking conductors to the right to which they are normally connected and connects them instead to theiincoming normal talking conductors 413 and 415. At its inner armatures, relay 505 disconnects the impulse conductors connected to the inner left-hand repeating-coil terminals from line relay 506 and connects them instead to relay 514 for a purpose which will be apparent as the description progresses. lVhen relay 501' operates over conductor 414 in multiple with relay 505, it groundsthe lower conductor of the toll trunk and connects ringing current to the upper conductor thereof, so as to apply ringingcurrent to the toll trunk to signal the toll operator in the operating center. In order to terminate the application of ringing current after a slight interval, relay 501 closesat its inner lower armature a circuit for the slow-to-pull-up relay 502. Relay 502 operates after a slight interval and closes a circuitfor the slow-to-pull-up relay 503, Relay'503 operates and locks itself to conductor 414, at the same time opening. the circuit of relay 5 01. Relay 501 falls back after a slight interval and removes the ringing current from the toll trunk, at the same time opening the circuit of relay 502. Relay 5'02'fa is back after a slight interval and opens the initial circuit of relay 503, leaving'relay 503 locked responds to theringing current placed on toll trunk No. I and repeated throug'l r theasso ciated repeating coil windings,- the lower windingof relay 11 5-bei-ng bridged across the talking conductors througlr contacts of cut off relay 1 14. Upon operating, relay locks itself through its upper winding and the upper contacts of the cutsofl!" rel ay. A circuit for the call lampat thetollbo'ardand fo'r'theone at the local board is closed in mul tiplewith the locking Winding off relay 115-; The operator at the local board does not ordinarily respondto the lighting of the call lamp on the toll trunk.

When the toll operator notes the lighted condition of the call lamp associated with the jack J2, she inserts the plug of an idle cord circuit into the ack, whereupona circuit is closed through the upper springs of the" jack for relay 113. Relay 113 isrend'e'red slightly slow-to-pull up due to the copper collar on its armature end as is denoted by the placing ofthe copper collar symbol on the upper end of the relay and by making the symbol blacli instead of shaded. Vhen relay 113 operates, a; circuit for the busy lamps" and fbr cut olf relay 114, whereupon the busy lampsbeeome lighted and relay 114 operates and cutsoiftlie lower winding of relay11'5, at the same time deenergizing the upper winding of the relay and extinguishing the call lamps. Relay 113 also connects relay'112 through contacts of the dial key 117 to the impulse conductors connected to the inne t'erminalsoftherighthand repeating coil windings. When this happens, relay 112 energizes through the right-hand repeatingcoil windings and over the toll line and closes a circuit f-orthe'as'sm ciated' supervisory lamp;

In the'SlAhhX. r'el'ay 514, 5, which is connected to the toll line'throi'igh the inner armatures of relay 505 contacts of relay 513, normal, and the left-hand repeating-coil windings, energizes series with relay 112, Fig. 1. Relay 514 closes a circuit forthe as sociated slow-acting relay 5 15, whereupon relay 5 15 operates and prepares a circuit for relay 504 so as to enable the localconnector to be released in a: manner tobe explained hereinafter.

After making a connection with; the toll trunk N0. 1 through the jack 12;,Fig. 1-,the toll operator converses with the calling subscriber and learns from him the destination of the call. In addition to ascertaining" the desired number, the toll operator enquires'as #1 to the number of the calling substation so that the proper charge may be made.

Afterlearning the desirednumbenjtlle toll operator completes the connection to the called line through-the upper'plug-ofhercord circuit in any well known or desired manner, whereupon the conversation may take pla c in the usual manner;

Inasmuch as the toll operator su ervises the toll connections rather closelyand listens foo in frequently to determine when the conversa tion has been finished, the subscribers may be instructed that it is unnecessary to ring off after a toll call, the toll connector is provided with arrangements tor releasing the local connector.

When the operator has listened in and has found that the conversation has terminated and that the subscribers have replaced their receivers, she withdrznvs the plug from the jack 32, Fig. 1, whereupon relay 113 falls back and opens the circuit of cut-oil relay 1141 and oi the busy lamps. Relay 113 also opens the circuit of relay 112, whereupon relay 112 falls back and opens the circuit of the associated lamp. lVhen the circuit of relay 112 is opened, relay 514, Fig. 5, which has been op erated in series with relay 112 and over the toll trunk, falls back. Relay 514 opens the circuit of the slow-acting relay 515, and relay 515 falls back a moment later. During the interval required for relay 515 to fall back after its circuit is opened, a circuit exists through the upper contacts of relays 015 and 514 for relay 504:, including the upper armature, normal, of relay 507 and the grounded private normal conductor 51-1. Relay 504 operates and places ground on normal conductor 413, at the same time placing battery through a low resistance on conductor 415. \Vhen this happens, a circuit is closed through the talking wipers 101 and 4103, Fig. 4t, of the local connector No. 1. and over conductors 353 and 357 for the release control relay 320 through contacts of ring-cut-ofl' relay 318. Relay 320 operates and initiates the releasing operation by closing the usual circuit for relay 311. The current flow over the calling line at this time is prevented by the condenser associated with the opened O-level shaft contacts 322. hen relay 515 falls back it opens the. circuit of relay 504, and relay 504. falls back after a slight interval and removes the battery and ground connections from conduct-ore 113 and 415. \V hen this occurs, relay 320 "falls back and the release of the connection takes place in the hereinbefore-described manner. \Vhen the ground potential is removed from the private normal conductor 414 upon the release of local connector No. 1, relays 503 and 505, Fig. 5, which have been held operated over this conductor, fall back. The connection is now released and the apparatus involved therein may be used in setting up other connections.

long-(listen 0e toll commotion It will now be assumed that the subscriber at substation A desires to converse with a subscriber located at a distance sufficiently great to bring the connection under the heading long distance. This call is initiated in the usual way and the local operator at the operating center dials the number 01 or the number 02, depending upon which of the toll trunks is idle, for example the toll trunk No. 1 (No. 01), whereupon the connection is completed by the local connector, for example the local connector No. 1, to the toll trunk No. l in the manner hereinbefore described. The socalled splash ring is transmitted over the toll trunk N o. 1 in the manner described hereinbefore to signal the toll operator. \Vhen the toll operator responds, the operations hereinbefore described take place and the calling subscriber is informed that he will be called back later. as the connection desired is a long distance connection that will require a certain amount of time to set up. The connection established with the toll operator is released in the hereii'ibetorc described manner when the toll operator removes her plug from the jack J2, Fig. 1.

After the operator has extended a connection to the desired line or has made sure that she can do so, she inserts the plug of a cord circuit into the jack of an idle one of the toll trunks, the ack J2 for example, whereupon relay 113 is operated from the jack contacts and closes the usual busylamp and cut-olfrelay circuit at its upper armature, at the same time connecting up relay 112 at it lower armatures to the impulsing conductors connected to the inner right-hand repeating-coil terminals. When this occurs, relay 112 operates over the toll trunk No. 1 and closes a circuit for the associatedsupervisorylamp.

In the S.A.M.X., line relay 506, which is normally connected to the toll trunk through the inner terminals of the associated lefthand repeating-coil windings, through the upper contacts of relay 513, and through the inner contacts of relay 505, operates in series with the calling supervisory relay 112, Fig. 1, and closes a. circuit for release relay 507. Release relay 507 opens a point in the associated release-magnet circuit when it energizes and it prepares the usual operating circuit at its lower armature. At its middle '11 ier armature rela Y 507 rounds the local locking conductor 5 11, and at its upper armature itdisconnects private normal conductor 11 1 from the local relays to which it is normally connected and connects it to ground instead, thereby rendering the toll trunk busy to the local connectors. 1

Having taken the toll trunk for use, the toll operator associates her calling device CD2 therewith by operating her calling device key 117. This key substitutes the circuit through the calling device CD2 and the release key RK2 for the branch circuit including relay 112. As a result relay 112 falls back when the dial key is thrown and the supervisory lamp is extinguished.

lVhen the operator dials the first digit in the number of the calling substation, the circuit of line relay 506, idig. 5, is interrupted a corresponding number of times. Relay 500 falls back each time its circuit is interrupted,

luL.

and, each time it does so, it transmits an impulse of current to vertical magnet 516, the circuit path over which the first impulse of current is transmitted including the lower armature, operated, of relay 507, the associated normally-closed off-normal contacts, and series relay 508. By the operation of the vertical magnet, the wipers 601-605. Fig. 6, are raised stepby-step until they arrive opposite the desired level of bank contacts. The sloiwacting series relay 508 operates when the first impulse is delivered and it remains operated throughout the vertical movement. Relay 508 serves to maintain its own circuit and that of the vertical magnet intact afterthe associated oil-normal springs have shifted upon the first oii-normal movement or" the switch. At the end of the vertical movement, relay 508 falls back and transfers the operating conductor through the normally-open off-normal contacts to the rotary magnet 518.

When the operator dials the next digit, the rotary magnet 518 responds by rotating the wipers 601 605, Fig. 6, into engagement with the contacts of the calling line, which is being recalled. Relay 511 operates in multiple with rotary magnet 518 when the first impulse is delivered to the rotary magnet, and, being slow-acting, remains operated throughout the rotary movement of the switch. At its inner upper armature, relay 511 disconnects the test wiper conductor 522 from the test winding of relay 512 and connects it instead to busy relay 510, and at its lower armature it places a shunt around the corresponding contacts of busy relay 510 so as to maintain its own circuit and that ofthe rotary magnet intact during the rotary movement in case busy relay 510 energizes due to test wiper 601, Fig. 6, passing over grounded test contacts.

The operations taking place at the end of the rotary movement depend upon whether the line being recalled has become busy in the interval or is still idle. If the line is busy, busy relay 510 is energized over conductor 522 and test wiper 601 at the end of the rotary movement, and when relay 511 falls back it completes the locking circuit of relay 510 to conductor 541, at the same time opening the impulsing circuit at its lower contacts to prevent further rotary movement. lVith the busy relay energized, a connection exists between the lower talking conductor and the busy-tone lead through the'lower contacts of the busy relay, and the upper talking conductor grounded at the upper contacts of the busy relay, affording a circuit path for the flow of busy-tone current through the right-hand repeating-coil windings, thus giving. the operator a busy signal.

Assumin now hatthe line is still idle 3 busy relay 510 is notoperated at the end of the rotary movement, and the falling back of relay 511 is followed by the energization of relay 512' through its test winding, the lower terminal of the test winding being connected to the grounded locking conductor 54:1 through the contacts of busy relay 510', and the upper terminal winding being connected to test wiper 602 through contacts of relay 511 and over conductor 522. Relay 512 energizes through the bank contact on which wiper" 602 is standing (such bank contact is omitted for convenience) and over the private normal conductor extending to the lineswitch. LS, Fig. 3. .Accordingly the cut-ofi winding 304 of the lineswitch LS energizes and disconnects relay 302 iirom in bridge of the line, but the pull-down armature is not operated owing to the relatively low strength of the cut-off winding,

In the toll connector, Fig. 5, when relay 512 operates it locks its lower winding to the grounded conductor 541 at its inner lower armature; connects the grounded conductor 541 directly with the test wiper conductor 522 at the adjacent armature so as to place direct ground potential on the test wiper; transfer the impulse conductor at another of its lower armatures from the rotary magnet 518 through contacts of relay 513 to the branch conductor 525 leading to the code selector CS2; and at its upper and lower armatures it connects up over conductors 520 and 527 the talking wipers 601 and 603.

When theoperator dials the code digit assigned to substation A,.the impules of current are transmitted over branch conductor 525 to the stepping magnet 610 of the code selector CS2 through contacts of relay 606 and through series relay 607. By the operation of the stepping magnet, wipers 612 and 61 3 are correctly positioned. Relay 507 is maintained operated throughout the last digit so" as to maintain the stepping circuit intact after the off-normal relay 606 has operated upon the first step of the switch. At the lower armature of off-normal relay 606, a circuit is prepared for release magnet 611, and a locking circuit for relays 608 and 609 is prepared at the upper armature of relay 606, a pick-up circuit being prepared at the inner upper armature of said relay.

At the end of the digit, relay 607 falls back and opens the impulse circuit, at the same time closing another point in the pick-up circuit. When the code-generator CG reaches its pick-up position, ground is placed on the pick-up conductor, closing a circuit for pickup relay 608, which relay operates and locks itself to the local locking conductor, at the same time opening its initial circuit. Relay 608 also prepares a circuit for stop relay 609 and connects up the wipers 612 and 613. The ringing current corresponding to the code assigned to substation A is placed on the line thereof during the further movement 

